The present invention generally relates to a component mounting apparatus and, more particularly, to a detecting device for the component mounting apparatus for detecting whether or not an electric component is, after having been mounted on a circuit board, fixed in position on the circuit board.
As used in describing and claiming the present invention, the term "electric component" is used to refer to an electric or electronic element, such as resistor, capacitor, diode or the like, of a type having at least one pair of terminal wires extending outwards from the body of the electric component.
With reference to FIGS. 1(a) and 1(b) of the accompanying drawings, the mounting of an electric component 2 on a printed circuit board 4 having a plurality of pairs of holes 6a and 6b is carried out by first transferring the electric component to a position immediately above the printed circuit board 4 with a pair of lead wires 8a and 8b aligned with a corresponding pair of the holes 6a and 6b, then pushing the electric component with a pushing member 10 so that the terminal wires 8a and 8b are inserted into the holes 6a and 6b, trimming excess portions of the terminal wires extending outwardly from the printed circuit board 4 in a direction opposite to the mounted electric component, and bending the trimmed terminal wires 8a and 8b sideways, preferably in a direction towards each other.
The bending of the trimmed terminal wires 8a and 8b is effected by a clinching mechanism including a pair of arms 12a and 12b supported by and pivotable about pins 14a and 14b, respectively. The contact between free ends of the terminal wires and slanted surfaces 16a and 16b of the arms 12a and 12b, respectively, holds the electric component 2 between the pushing member 10 and respective arms 12a and 12b, and bends the end portions of the terminal wires. Thereafter, clockwise and counterclockwise rotation of the arms 12a and 12b about the pins 14a and 14b, respectively, causes upper end portions of the associated arms 12a and 12b to bend the free end portions of the terminal wires extending outwardly from the printed circuit board 4, whereby the electric component 2 is fixedly mounted on the circuit board 4 as shown in FIG. 1(b).
During the mounting of the electric component 2 on the circuit board 4 in the manner described above, the component mounting apparatus may fail to mount the electric component fixedly on the circuit board, unless the terminal wires are properly inserted into the holes in the circuit board, or unless the electric component has terminal wires of sufficient length.
Because of such a failure in the operation of the component mounting apparatus, there is provided a detecting device in the component mounting apparatus for detecting whether or not the electric component is properly fixed in position on the circuit board.
Referring again to FIGS. 1(a) and 1(b), the conventional type detecting device of includes an electrical power source such as batteries 18a and 18b and current detecting circuits 20a and 20b. The battery 18a and the current detecting circuit 20a are connected in series between the pushing member 10 and the arm 12a which are made of electrically conductive material whereas the battery 18b and the current detecting circuit 20b are connected in series between the pushing member 10 and the arm 12b. When the electric component 2 has the terminal wires thereof properly inserted into the corresponding holes 6a and 6b and when the terminal wires 8a and 8b are subsequently held in contact with and between the pushing member 10 and the arms 12a and 12b, a first closed electrical circuit is established through the battery 18a, the pushing member 10, the terminal wire 8a, the arm 12a and the current detecting circuit 20a and, at the same time, a second closed electrical circuit is established through the battery 18b, the pushing member 10, the terminal wire 8b, the arm 12b and the current detecting circuit 20b. Upon establishment of the first and second closed electrical circuits, each of the current detecting circuits 20a and 20b produces a signal indicating that the electric component 2 is properly mounted on the circuit board. By the utilization of this electric signal, the component mounting apparatus can proceed to mount the electric component.
On the contrary, when at least one of the terminal wires 8a and 8b is not properly inserted into the corresponding hole, said terminal wire will not electrically connect the pushing member 10 to the arm. Therefore, either the first and second circuit will be open and, therefore, the corresponding current detecting circuit will produce a warning signal which is utilized to interrupt the apparatus to prevent further operation.
For the purpose of ensuring the establishment of the first and second circuits independently from each other, the arms 12a and 12b are electrically insulated from each other. Therefore, the arms 12a and 12b are insulated from the respective pins 14a and 14b and means (not shown) for rotating the arms 12a and 12b. However, there is a disadvantage to this arrangement in that the insulation of arms 12a and 12b not only complicates the structure of the arms 12a and 12b, but also requires a careful maintenance of the arms 12a and 12b and the concurrent use of means for preventing the arms 12a and 12b from collecting dust and metallic particles which may cause deterioration of the insulation.
Furthermore, there is also a disadvantage that in the case where the terminal wires are coated with insulating material for some reason or by the overflow of the insulating material coated around the body of the electric component, the electric connection between the pushing member 10 and the terminal wires not take place and the above described closed circuits cannot be established. Therefore, even if the electric component is properly mounted on the circuit board, the current detecting circuits may produce the warning signal.
Moreover, there is a disadvantage that the electric component itself will be adversely affected by current flowing through any one of the above described closed circuits.